Polymer compatibility and biodegradation of starch–poly(ethylene‐co‐acrylic acid)–polyethylene blends

X‐ray diffraction, CP/MAS C‐13 NMR, DSC, FTIR and fluorescence microscopy have been used to study the structure, compatibility, and morphology of films made from starch, poly(ethylene‐co‐acrylic acid) (EAA), and polyethylene (PE) before and after exposure to a mixture of highly amylolytic bacteria. The components of starch, amylose and amylopectin, interact with EAA via the formation of V‐type inclusion complexes and hydrogen bonds. PE appears to be immiscible with the starch–EAA complex, with each forming sheetlike domains. The amylopectin in the films is susceptible to digestion by the bacterial consortium while the crystalline EAA–amylose complex is resistant. Digestion begins at the film surface and then proceeds inwards with sheetlike areas of starch removed. The good compatibility between starch and EAA as well as migration of EAA to the film surface explains the resistance of such films to digestion by conventional amylases.